ANKARA (Reuters) - Turkey’s pro-Kurdish opposition party said on Wednesday it would nominate former co-leader Selahattin Demirtas, who is jailed on security charges, to run for president in the June 24 snap election.

Demirtas’s People’s Democratic Party (HDP) commands only about 10-12 percent support, but he is still likely to draw significant backing in a first round presidential vote against President Tayyip Erdogan and other candidates.

Pollsters also say that as a presidential candidate Demirtas would probably the boost the prospects of the HDP in the parliamentary part of the June 24 election.

Demirtas, one of Turkey’s best-known politicians, won votes beyond his Kurdish core constituency in recent elections and in 2015 helped make the HDP the second biggest opposition force in parliament.

“We are coming together to share our joy in Selahattin Demirtas’s candidacy for president,” the party’s current leaders said in a letter inviting supporters to a rally on Friday where the formal announcement of Demirtas’s candidacy will be made.

The HDP had said last week it was highly likely that Demirtas would be nominated and one of his lawyers on Wednesday told Reuters there was no legal obstacle to him standing despite ongoing legal cases against him.

Demirtas is charged with links to the outlawed Kurdistan Workers Party (PKK) and faces up to 142 years in jail if convicted. Turkish law bars those convicted of terrorism charges from running in elections. He has denied the charges.

Nine other members of the HDP have also been jailed, convicted or are awaiting trial for alleged links to PKK militants. The HDP denies direct ties to the PKK, which has been waging an insurgency in the mainly Kurdish southeast since 1984.

The two other main opposition parties, the Republican People’s Party (CHP) and the fledgling Iyi (Good) Party, have decided to join two smaller groups in an election alliance, a CHP official said on Wednesday.

The deal with the Islamist Saadet Party and the Democrat Party creates a broad coalition against Erdogan’s ruling alliance and will enable the two smaller parties to sidestep a 10 percent threshold needed to enter parliament.